Benzothiazole-2-dimethylsulfinamide and process for preparing the same



Patented Feb. 12, 1952 BENZOTHIAZOLE- 2 -DIMETHYLSULFIN- AMIDE AND PROCESS FOR PREPARING THE Georges Mingasson, Paris, France, a'ssi'gnor to =Soc1eteAnonyme de Matieres Colorantes et Produits Chlmiques Francolor, Paris, France,

a French company No Drawing. Application October 29, 1949,

Serial No. 124,478

6 Claims. :1 This invention relates to the production .of an organic compound containing nitrogen, sulphur and-oxygen and to its'use as a vulcanisation accelerator.

The present application is a continuation-in part of application Serial No.9,342,fil'e'dFebruary 18, 1-948, now abandoned;

There have already been described products resulting from the action of oxidising agents on mixtures of secondary amines and 2-mercaptobenzothiazole or 2 2-dibenzothiazyldisulphide.

This reaction has already been studied in the caseofa great number of secondary amines and hasalready formed the subject ofsevera'l patents, in particular United States Patent No. 2,417,989, dated March .25, 1947, and United States Patent No. 2,419,283, dated April 22, 1947,. Experiments made up to the present have led solely to substances containing carbon, hydrogen, nitrogen andsulphur, whichhave generally been considered to be thiazylsulphenam-ides. 'For example, starting from 2-mercaptobenzonthiazole, the reaction proceeds according to the folowing Equa: tion I:

R-.SH HN\ RI! wherein R is a benzothiazyl radical, R is hydrogen or a hydrocarbon radical and R" is a hydrocarbon radical.

Among the secondary, amines to be employed in this reactiondimethylamine has beenmentioned,

but there have never been given any precise in- (1) An excess of dimethylamine must be used,

that is to-say, ,a quantity exceeding 1 gram .mole culefor each gram molecule of 2-mercaptobenzothiazole, or of each gramnmolecule of 2:2- dibenzothiazy-ldisulphide. It is thus necessary to use more than one molecular part of dimethylamine for each molecular part of benzothiazole combined in the sulphur compound. e. for each two atoms of sulphur contained in the sulphur compound I (2) In thecase where theoxidation of the mixture is effected with hypochlorite of an alkali metal such volume of reagents is used that for each gram molecule of dimethylamine taken, the volume of; the mixture at the end of the reaction is less than 7000.0.

The reaction mixture :may contain, in addition 'It'is formed according to the following Equa tion II-or Equation III, depending upon whether there is used as the starting material'la' merca'ptobenzothiazole or 2:2 -dibenzothiazyldisulphide On studying the oxidation. of a mixture o'fzmercaptobenzothiazole and dimethylamine by (III) sodium hypochlorite, it hasbeen noted that by effecting the reaction under some conditions slightly diflferent from those just indicated above,

there can be obtained (in addition to the oxygenated substance of the present invention) .a variable quantity of an oily substance, apparently formed according to Equation I, which by i e-crystallisation from petrol ether givesa crystalline product very soluble in the cold in alcohol and ether, melting at 37 C. and having an analysis. which indicates. an empirical formulaCsHmNzSa It does notcontain any oxygen and is apparentlyv composed of thedimethylbenzothiazole-Z-sulphenamide whose preparation by a difierent process is described in C lerman stance of the formula C9H10ON2S2 is favoured by a high concentration of dimethylamine. The preparation of either of these products is thus effected under conditions unfavourable for the production of the other. The yield of the new substance of the formula C9H10ON2S2 increases as the quantity of oxidising agent is increased beyond that necessary for the formation of the sulphenamide and attains its maximum with double that quantity, that is to say, when that quantity is reached which is theoretically necessary for the formation of the new substance.

As has already been indicated above, the new substance of the present invention is distinguished from the dimethylbenzothiazole-2-sul phenamide previously described, by the fact that it contains oxygen, as is shown clearly by the following analysis:

H s N o 43.1 4. 53 28.3 11.85 7. 22 Fmmd 47.9 4. 51 28.6 11. 92 7. 07 Calculated for minnows," 47. 78 4. 42 28.31 12. 38 7. 07

I By difference.

By the action of dilute caustic soda in the hot the new substance of the invention gives 2-hydroxy-benzothiazole, orthoaminothiophenol, sodium sulphite and sodium sulphide and, quantitatively, dimethylamine.

The known substance, dimethylbenzothiazolez-sulphenamide is immediately decomposed by the action of dilute hydrochloric acid in the cold into 2:2-dibenzothiazldisulphide and dimethylamine hydrochloride without the formation of appreciable quantities of sulphur dioxide.

The new substance forms an excellent vulcanisation accelerator for natural as well as synthetic rubber. It is distinguished from the-usual accelerators by the fact that it only begins to react at relatively high temperatures, so that its use is very safe. It gives the vulcanisates excellent mechanical properties. It is distinguished from the sulphenamides prepared with the lower members of the series of secondary aliphatic amines by its greater stability and its crystalline form, which allows of its being obtained in a greater state of purity.

The-figures given in the following table con-- firm the superiority of the new substance according to the invention in contrast to benzothiazole--' 2-diethylsulphenamide which is one of the most important vulcanisation accelerators in the class of sulphenamides.

Curing time in minutes- Composition of the mixture used for the tests in the above table:

Parts by weight Natural rubber (smoked sheets) 100 Zinc oxide 5 Sulphur 3 Stearic acid 1 For the test I described in the above table the mixture also contained one part by weight of the new product of the invention. For the test II of the above table the mixture also contained instead of the product of the invention one part by weight of commercial benzothiazole-Z- diethylsulphenamide.

In the examples of the preparation and use of this substance, given hereinafter in an illustrative and not limiting way, the parts by weight may be in any units, and where some parts are by weight and others by volume, one part by volume is the volume of one partby weight of water.

Example I To a solution of 16.7 parts by weight of 2-mercaptobenzothiazole in 42 parts by volume of a. solution in water of dimethylamine containing 380 grams per litre there is added all at once a 24 hours. After this time, the crystalline magma which is formed is filtered oif, then this magma is washed and dried. There is thus obtained the new substance of the invention which has the characteristics set forth above.

Example II To a solution of 16.7 parts by weight of 2-mercaptobenzothiazole in 15 parts by volume of a solution of dimethylamine containing 450 grams of base per litre'there is added, while mixing, 10 parts by weight of solid sodium chlorite (85% NaC'lO2). The temperature is maintained at about 40 C. until the oxidation has been completed. The product of reaction separates in crystalline form and has the characteristics of the new substance of the invention.

Example III To a solution of 16.7 parts by weight of 2-mer- 1 rates in crystalline form in the course of the addition and is isolated as described in Example I.-'

Example IV To-a solution of .334 parts by weight-of 2- assumesmercaptobenzothiazole in 60 parts by -'volume= of anaqueous solution of dimethylamine containing 450 grams of the base per litre there is'int'roduced with mixingovera period of three to four hours andat about 30 C. 150 parts by volume of a-solution' of sodium hypochlorite' containing 1-0" The product oi grams of NaClO per 100 -c. the-reaction precipitates'in' crystalline form in the course of the addition. When all the hypochlorite has been'used'up the product is filtered, washed with: water and dried;v The product obtained possesses the same characteristics-as the product obtained. according. to each ofthe preceding examples.

ErampleV 1rd a solution of 334 parts by weightor 2 mercaptobenzothiazole in-50 parts by volume-of anaqueous solution ofdimethylamine containing 450 grams of the base per litre there are added over 4 hours at a temperature of C. 68 parts by volume of an aqueous solution of hydrogen peroxide containing 20 grams of H202 per 100 c. c. There separates a crystalline product the same as that of the preceding examples.

Example VI There are first dissolved 16.6 parts by weight of 2:2-dibenzothiazyldisulphide in parts by volume of an aqueous solution of dimethylamine containing 450 grams of the base per litre. There is added to this solution a solution of 8.3 parts by weight of sodium chlorite (82% NaClOz) in 15 parts by weight of water at a temperature of to C. which is maintained for 24 hours. There separates the same product as that obtained in each of the preceding examples.

Example VII There are dissolved 16.6 parts by weight of,

2:2-dibenzothiazyldisulphide in 32 parts by volume of a solution in water of dimethylamine (43% by volume). There are slowly added 52 parts by weight of 10% aqueous hydrogen peroxide. The product which is precipitated in the crystalline state is isolated as described in Example I.

Example VIII The following mixture is prepared:

Parts by weight Natural rubber (smoked sheets) 100 Zinc oxide 5 Sulphur 3 Stearic acid 1 Product prepared according to the invention 1 The mixture is vulcanised at 130 C. for 45 minutes.

The vulcanisate has a breaking stress of 250 kg./cm. with an elongation of 665%.

Example IX The following mixture is prepared:

Parts by weight Natural rubber 100 Cosmobile black Pine tar 5 Zinc oxide 5 Sulphur 2.5 Stearic acid 2 Product prepared according to the inven- 1 .0

tion

utes the rubber is not vulcanizedl If on the contrary it-i's. heated foi l5 minutes to 140 C. vulcanisation occurs und'er" excellent conditions and the vulcanisate has a breaking stress of 230 kg./cm. with an elongation of 580%. If it is heated to 140. C. for 30 minutes the vulcanisate obtained has a breaking stress of 240 kg./cm. with an elongation of-535 Example X I The .natural rubber in the mixture according to Example IX is replaced by synthetic rubber'ofj the type known iniindustry' under the name of Gift-S.v

By heating the mixture for a breaking'stress of 148'kg./cm. with an'elongation of 476%.

If the mixture. is heated to 125 C. only, no vulcanisation occurs.

I declare that what I claim is:

1. As a newproduct, benzothiazole-2-dimethylsulphinamide in the form .of crystals melting at about 125 C. and having the following formula:

c-so-n 2. The process for the preparation of a product of the following formula:

which comprises treating with sodium chlorite 2- mercaptobenzothiazole in the presence of a concentrated aqueous solution of dimethylamine, at

a temperature of approximately 40 C., the quantity of dimethylamine being about .16 parts by weight for 16.7 parts by weight of the 2-mer captobenzothiazole.

4. A process for the preparation of a product of the following formula:

which comprises treating. with sodium chlorite 2- mercaptobenzothiazole in the presence of a concentrated aqueous solution of dimethylamine, at a temperature of approximately 40 C., the quantity of dimethylamine being about 6.7 parts by 30. minutes to C. there is obtained a vulcanisate which hasweight for 16.7 parts by weight of the 2-mercaptobenzothiazole.

' 5. A process for the preparation of a product of the following formula:

C-BO-N which comprises treating with sodium chlorite 2- mercaptobenzothiazole in the presence of a concentrated aqueous solution of dimethylamine, at a temperature of approximately 60 C., the quantity of dimethylamine being about 11.25 parts by weight for 16.7 parts by weight of the 2-mercaptobenzothiazole.

8. A process for the preparation of a product of the following formula:

which comprises treating with-sodium chlorite 2,2-dibenzothiazyldisulphide in the presence of a concentrated aqueous solution of dimethylamine, at a. temperature of approximately 40-45 C. the quantity of dimethylamine being about 13.5 parts by weight for 16.6 parts by weight of the 2,2-dibenzothiazyldisulphide.

REFERENCES CITED The following references are of record in 'th file of this patent:

UNITED STATES PATENTS GEORGES MINGASSON. 

1. AS A NEW PRODUCT, BENZOTHIAZOLE-2-DIMETHYLSULPHINAMIDE IN THE FORM OF CRYSTALS MELTING AT ABOUT 125* C. AND HAVING THE FOLLOWING FORMULA: 